Contact arrangements in oil circuit interrupter



W. E. HARPER July 16, 1968 CONTACT ARRANGEMENTS IN OIL CIRCUIT INTERRUPTER 3 Sheets-Sheet 1 Filed Dec.

awn/150k JQXi DRM/ J July 16, 1968 w. E- HARPER 3,393,285

CONTACT ARRANGEMENTS IN OIL CIRCUIT INTERRUPTER Filed Dec. 30, 1965 3 Sheets-Sheet 13 July 16, 1968 w. E. HARPER 3,393,285

CONTACT ARRANGEMENTS IN OIL CIRCUIT INTERRUPTER Filed Dec. 30, 1965 3 Sheets-Sheet s 2a zamzzg,

United States Patent 3,393,285 CONTACT ARRANGEMENTS IN OIL CIRCUIT INTERRUPTER William E. Harper, Walpole, Mass., assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Dec. 30, 1965, Ser. No. 517,705 9 Claims. (Cl. 200150) This invention relates generally to electrical circuit interrupters such as high speed oil circuit breakers of the fluid blast type. [More specifically, it relates to improvements in the arrangement and construction of the arc extinguishing or interrupting devices used in such circuit breakers.

.Modern oil circuit breakers usually comprise a plurality of pairs of series connected separable main contacts for each phase or line of an electric circuit being protected. Typically, one contact of each pair of main contacts is stationarily mounted within a main are extinguishing device and cooperates with a bayonet type contact which is movable into and out of the device. The extinguishing device is submerged in an arc extinguishing fluid such as oil which aids in arc extinction.

Performance of such oil circuit breakers can be improved in several ways including the following:

(a) By providing means within the main arc extinguishing device to force are extinguishing fluid through the are generated therein;

(b) By connecting a high or intermediate ohmic value shunt resistor across each pair of main contacts to equalize the division of recovery voltages across each pair of main contacts;

(0) By connecting a low ohmic value shunt resistor across each pair of main contacts to limit switching Surge voltages; and

(d) By connecting a pair of separable auxiliary contacts in parallel with one or more pairs of main contacts to provide an additional current path.

The above listed improvements are more particularly discussed as follows:

(a) For example, piston means located inside of the arc extinguishing device and operable in response to movement of the bayonet contact forces oil through the are as the arc is generated.

(b) Connection of a high ohmic value shunt resistor (about 50,000 ohms) in shunt across each pair of series connected main contacts equalizes the division of recovery voltage across each pair. In practice the resistor has one end electrically connected to the stationary main contactand the other to a resistor probe. The probe is in electrical contact with the movable bayonet contact after the latter has disengaged the stationary main contact and thus the resistor is in circuit after the pair of main contacts open. The are formed as the probe and bayonet separate is not severe and can be extinguished in unconfined oil outside the extinguishing device. High ohmic value shunt resistors may be replaced by medium or moderate ohmic value resistors (about 800 ohms) for special applications such as switching capacitive currents, but the manner of interrupting the resistor arc remains the same.

(c) On many modern transmission systems, especially those at 345 kv. and above, it is particularly important that, in addition to controlling recovery voltages, switching surge voltages be limited to crest values equal to approximately twice the peak value of the normal phaseto-ground voltage. This can be accomplished by connecting a low ohmic value shunt resistor (about 350 400 ohms, for example) in parallel with the main contacts so that the electrical circuit is energized momentarily through the low ohmic value resistor before closing the ice main contacts of the breaker. The resistors used usually have an aggregate value approximately equal'to the surge impedance of the system. This low value of shunt resistance results in a resistor current in the range of 1600 amperes when the breaker is switching a short circuit. For switching such values of resistor current, a break between the resistor probe and the movable bayonet contact in free oil requires long are lengths and gives long are durations. This results in the creation of a dielectric hazard due to the long arc lengths, and high energy dissipation in the resistor due to long are durations. Both conditions are detrimental to economical manufacture and reliable performance of the breaker and suitable arc extinguishing means are required.

(d) Finally, the short circuit and continuous current carrying capacity of the circuit breakers can be improved by connecting a pair of separable auxiliary contacts in parallel with one or more pairs of main contacts. The auxiliary contacts open before and close after the associated main contacts and, consequently, no arcing normally occurs between the auxiliary contacts but only between the main contacts. The auxiliary contacts are constructed, however, to have superior current carrying and heat dissipating ability when closed and are designed to carry the larger portion of continuous load and short circuit current.

It is an object of the present invention to provide an improved high speed oil circuit breaker which employs main contacts and auxiliary contacts to increase the current carrying capacity of the breaker and which further employs high (or intermediate) and low ohmic value resistors in shunt with the contacts to equalize recovery voltage and to limit surge voltages, respectively, during switching.

Another object is to provide such a circuit breaker which employs only low ohmic value resistors in shunt with each pair of main and auxiliary contacts.

Another object is to provide such a circuit breaker wherein the main interrupter device, and the associated auxiliary interrupter device, surge limiting resistor, and voltage dividing resistor (if used) are suspended from a metallic platform member to comprise a modular interrupter assembly which effects economies in space and materials and which provides improved heat transfer from the components to the surrounding oil.

Another object is to provide such a circuit breaker wherein the auxiliary contacts and the means for switching the low ohmic value surge limiting resistor are mounted in improved auxiliary interrupter devices having oil impulse arc extinguishing means for effecting interruption of the resistor arc.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate preferred embodiments of the invention but it is to be understood that the embodiments illustrated are susceptible of modifications with respect to details thereof without departing from the scope of the appended claims.

In the drawings:

FIG. 1 is an elevational view partly in section of a circuit breaker shown in circuit closed position and employing one embodiment of the present invention;

FIG. 2 is an enlarged view, partly in section through one of the main and one of the auxiliary interrupter devices shown in FIG. 1;

FIG. 3 is a top plan view of the component shown in FIG. 2;

FIG. 4 is a view similar to FIG. 2 but showing the circuit breaker in circuit open position; and

FIG. 5 is an elevational view partly in section of another embodiment of an auxiliary interrupter in accordance with the present invention, showing the interrupter in open position.

Referring to the drawing, FIG. 1 illustrates an oil circuit breaker such as is used in high voltage electric power transmission systems. The circuit breaker comprises a tank which is filled to a level 12 with are extinguishing fluid such as oil. A pair of terminal bushings 14 and 16 are supported by and extend into tank 10 and are extinguishing assemblies 18 and 19 depend from the lower ends of the bushings 14 and 16, respectively.

FIGS. 1, 2 and 2 show that are extinguishing assembly 18 comprises an electrical conductive platform member or casting 24, and suspended therefrom are a main arc interrupter 26, an auxiliary arc interrupter 28, a voltage dividing resistor 30, and a surge limiting resistor 32.

Arc extingushing assembly 19 is identical to assembly 18 in that it comprises a platform casting 24a, main and auxiliary interrupters 26a and 28a, respectively, and voltage dividing and surge limiting resistors 30a and 32a, respectively. Therefore, only assembly 18 will hereinafter be described in detail.

A conductive bridge shown in closed position in FIG. 1 and having bayonet contacts thereon connects the assemblies 18 and 19. Bridge 20 is supported by and is reciprocably movable vertically by an insulated lift rod 22 to open and closed positions. Bridge 20 comprises a main bayonet contact 21 and an auxiliary bayonet contact 23 at one end of association with main and auxiliary interrupters 26 and 28, respectively, and comprise similar main and auxiliary bayonet contacts at its other end. The contact penetration of the main bayonet 21 into its associated interrupter is greater in the arrangement shown than that of the auxiliary bayonet 23 into its associated interrupter.

Referring to arc extinguishing assembly 18, platform casting 24 is electrically and mechanically connected to terminal bushing 14 and, in addition to serving as a support and an electrical connector, serves as a heat sink for the interrupters and resistors associated therewith and radiates and conducts this heat to the surrounding oil by conduction, convention and radiation. Platform casting 24 also serves as an electrode with large radii to reduce the electrical voltage gradients around the upper end of the interrupting unit and stationary auxiliary contact, thus increasing the dielectric strength of the breaker.

Main arc interrupter 26 comprises a metallic top section 34 and an insulating lower section 36. Top section 34 is electrically and mechanically connected to platform casting 24. A stationary main contact 38 is located in main interrupter 26 and is electrically connected to top section 34. Lower section 36 of main interrupter 26 is adapted to confine and extinguish arcing that occurs therein. Reference may be had to US. Patent 3,067,307 for Fluid Blast Interrupting Device for Oil Circuit Breakers issued Dec. 4, 1962, to I. M. Ramrath and assigned to the same assignee as the present application for a detailed description of a type of interrupting device similar to main interrupter 26.

A shunt resistor 30 of high or moderate ohmic value is mounted on casting 24 and is supported against lateral movement by a bracket 31 connected to a bottom plate 42 on interrupter 26. The upper end of resistor 30 is electrically connected to casting 24. Bracket 31 also serves as the electrical connection between the lower end of shunt resistor 30 and bottom plate 42 of interrupter 26. Plate 42 also performs the function of a resistor probe to insert the shunt resistor into the electrical circuit when the interruption of the power arc occurs in the main interrupter. Plate 42 is provided with a hole 44 for accommodating movable contact 21.

In accordance with one embodiment of the invention, auxiliary interrupter 28 comprises a metallic top section 46 having oil refill ports 47 and an insulating lower section 48 having a nozzle section 49. Top section 46 is lectrically and mechanically connected to platform casting 24. The

4- v, lower end of auxiliary interrupter 28 is enclosed by an insulating bottom plate 51 which serves as the lower'end of a pressure vessel. Bottom plate 51 has a hole which admits the auxiliary bayonet contact 23 into auxiliary interrupter 28 and which serves as an orifice for the passage of fluid. A stationary auxiliary contact 50 is located in auxiliary interrupter 28 and mounted on an electrically conductive spider 57 which iselectrically connected to metallic top section 46. Stationary contact 50 comprises a housing 53 in which there are a plurality of spring biased contact fingers 54 which make sliding contact with auxiliary bayonet contact 23.

A11 oil pumping piston 56 is slidably mounted for axial movement in top section 46 of auxiliary interrupter 28. Piston 56 has ports 58 for passing fluid from one side to the other thereof and is further provided with a vent 60 through its top. A spring 62 is disposed between piston 56 and an upper end wall 64 of auxiliary interrupter 28 and tends to bias the piston downwardly (with respect to FIG. 2).

An electrically nonconductive piston push rod 66 is slidably mounted for axial movement in housing 53 of auxiliary contact 50. The upper end of piston rod 66 bears against piston 56 and the lower end bears against bayonet contact 23.

The lower section 48 of auxiliary interrupter 28 accommodates an electrically conductive resistor probe 78. Probe 78 has an opening for accomodating bayonet contact 23. Resistor probe 78 extends outside of interrupter 28' and is electrically and mechanically connected to one end of surge limiting resistor 32. The other end of resistor 32 is electrically and mechanically connected to platform casting 24.

The circuit breaker employing main and auxiliary interrupters such as 36 and 28, respectively, operates as follows. Assume first that bridge 20 is in open position as shown in FIG. 4 and that it is to be moved to closed position shown in FIGS. 1 and 2 by upward movement of lift rod 22. Since the components in the arc extinguishing assemblies 18 and 19 operate in the same way, only the operation of assembly 18 will hereinafter be described in detail. During the closing stroke of the circuit breaker, the tip of main bayonet contact 21 enters main interrupter 26 through hole 44 in bottom plate 42. At this point, shunt resistor 30 is inserted into the circuit for equalizing the voltage drop across each pair of main contacts. At about the same point in the stroke, the auxiliary bayonet contact 23 enters lower chamber 74 of auxiliary interrupter 28.

As the closing stroke continues, auxiliary bayonet contact 23 approaches resistor probe 78. As this occurs, prestriking of the electric arc from the tip of auxiliary bayonet contact 23 to resistor probe 78 is minimized because the voltage-dividing network formed by high. ohmic value shunt resistor 30 divides the voltage equally between each series gap. A continuation of the closing stroke causes low ohmic value surge limiting resistor 32 to be inserted into the circuit, damping out the closing surges as previously described.

Resistors 30 and 32 remain in the circuit during the time the bayonet contacts 21 and 23, respectively, traverse the length of main interrupter 26 and auxiliary interrupter 28.

A minimum of one-half cycle later, the power circuit is closed as main bayonet contact 21 engages main interrupter contact 38. As main bayonet contact 21 nears the end of its closing stroke, it makes contact with main interrupter contact 38. At this point, resistor 30 is shunted out and the circuit is energized directly through the main contacts of the breaker. The final event of the closing stroke is the engagement of auxiliary bayonet contact 23 with auxiliary interrupter contact 50 less than one-quarter cycle after the closing of the main interrupter contacts and the compression of the piston springsas previously described. Thus, the auxiliary contacts and the main contacts share the burden of carrying both continuous and short circuit currents when the breaker is in the fully closed position.

During the time auxiliary bayonet contact 23 has been traversing the length of auxiliary interrupter 28, auxiliary bayonet contact 23 passes through opening 80 of resistor probe 78 and enters contact housing 53 of contact 50, As auxiliary bayonet contact 23 nears the end of its closing stroke, its upper end butts against the lower end of piston push rod 66 and quickly pushes it upward, causing piston 56 to move upward compressing piston spring 62. The oil above piston 56 displaced by upward piston movement is driven out through the refill ports 47. When the breaker is in the closed position, piston spring 62 is held in compression and is charged with mechanical energy.

The breaker is opened by downward movement of lift rod 22 which causes the bridge 20 to descend, initiating withdrawal movement of both bayonet contacts 21 and 23 from the interrupters 26 and 28, respectively. On opening, the auxiliary contacts 23 and 50 are the first to part, so there is no power are established in auxiliary interrupter 28.

For the first portion of the opening stroke of auxiliary bayonet contact 23 (approximately inch in one actual embodiment) piston spring 62 acting through piston 56 and push rod 66 accelerates the auxiliary bayonet contact to aid in getting the contact up to its required opening velocity quickly. During this portion of the stroke, hydraulic impedance to piston movement is minimized by allowing the oil under piston 56 to flow freely out of auxiliary interrupter 28 through the refill ports 47. When piston 56 reaches the lower edge of the refill ports 47, the piston movement is slowed down until nozzle section 49 is opened by withdrawal of auxiliary bayonet contact 23 during the latter portion of its stroke.

As auxiliary bayonet contact 23 continues its opening stroke, it withdraws from contact housing 53. The main interrupter contacts 21 and 38 are next to part, drawing a power are within main interrupter 26. Once this are is extinguished, the recovery voltage causes the low ohmic value resistor circuit to come into conduction. This shunt resistor circuit has the twofold benefit of damping the voltage surges resulting from the interruption of the power arcs, and reduces the recovery voltage impressed across the main interrupting devices, thus reducing any tendency toward resriking of the arcs, and damping any surge voltages that would occur in the event such restrikes did take place. This benefit is especially important during the switching of capacitive currents such as occur with unloaded transmisison lines or static capacitor banks.

As the tip of auxiliary bayonet contact 23 is withdrawn from orifice 80 in resistor probe 78, an electric arc is drawn between the probe and the bayonet tip. Then, after the tip of auxiliary bayonet contact 23 disengages resistor probe 78, piston 56 begins to descend more rapidly forcing oil through opening 80, through nozzle 49, and then through orifice 55 in bottom plate '51 as the receding bayonet tip opens up each of these passages in turn. This flow of oil creates a cross-blast flow against the arc tending to cause its extinction. As auxiliary bayonet contact 23 continues its opening stroke, its tip passes through hole 55 in bottom plate 51. At this point, piston 56 is free to drive oil from pressure chamber 74 through orifice 55 into tank of the breaker. This flow of oil through orifice 55 establishes an axial blast of oil against the are (a flow of oil coaxial with the arc and impinging on the are within the orifice). This creates a second zone of arc interruption. The interruption of the resistor are then occurs at the next natural current zero thus completing the second stage of interruption and effecting the electrical isolation of the circuit.

In the event of a high current (short-circuit) interruption, the power arc in main interrupter 26 may not be interrupted early enough during the opening stroke to insert low ohmic value shunt resistor 32 into the circuit.

In this case, shunt resistor 30 provides the voltage equalization function for the power arc interruption instead of the interruption of the arc in the low ohmic value shunt resistor circuit.

As the opening stroke continues, the tip of main interrupter bayonet contact 21 is withdrawn from its main interrupter 26. A this point, an arc is established between the tip of main interrupter bayonet contact 21 and main interrupter bottom plate 42 to disconnect high ohmic value resistor 30. Since the arc current is very low, this arc is readily inerrupted in the oil-filled gap between the tip of bayonet contact 21 and bottom plate 42 as the bayonet contacts of the breaker continue their stroke to the full open position.

In some applications the high ohmic value resistor 30 may be eliminated from the structure, but taking this fact into account, operation of the circuit interrupter is substantially as hereinbefore described.

FIG. 5 shows another embodiment of an auxiliary interrupter designated by the numeral 128 which may be employed in a circuit breaker according to the present invention. Auxiliary interrupter 128 is understood to operate in the circuit in the same manner as auxiliary interrupter 28 hereinbefore described but has a diflerent mode of operation internally. Auxiliary interrupter 128 comprises a metallic top section 146 having oil refill ports 147 and an insulating lower section 148 having a nozzle section 149. Top section 146 is electrically and mechanically connected to platform casting 24. The lower end of auxiliary interrupter 128 is enclosed by an insulating bottom plate 151 which serves as the lower end of a pressure vessel. Bottom plate 151 has a hole which admits the auxiliary bayonet contact 23 into auxiliary interrupter 128 and which serves as an orifice for the passage of fluid. A stationary auxiliary contact 150 is located in auxiliary interrupter 128 and mounted on an electrical conductive spider 157 which is electrically connected to metallic top section 146. Stationary contact 150 comprises a contact housing 153 in which there are a plurality of spring biased contact fingers 154 which make sliding contact with auxiliary bayonet contact 23.

An oil pumping piston 156 is slidably mounted for axial movement in top section 146 of auxiliary interrupter 128. Piston 156 has ports 158 for passing fluid from one side to the other thereof and is further provided with a vent 160 through its top. A spring 162 is disposed between piston 156 and an upper end wall 164 of auxiliary interrupter 128 and tends to bias the piston downwardly (with respect to FIG. 5).

An electrically nonconductive piston push rod 166 is slidably mounted for axial movement in housing 153 of auxiliary stationary contact 150. The upper end of piston rod 166 bears against piston 156 and the lower end is adapted to move through contact housing 153 and bear against bayonet contact 23. Piston rod 166 has an oil flow passage 168 extending axially therethrough which is in alignment with vent 160 in piston 156 and a free floating ball valve 170 is located in a cage 159 formed between the upper end of piston 156 and piston rod 166 to serve as a one-way valve means for preventing the downward flow of fluid through the passage but permitting upward flow, as hereinafter described.

The lower section 148 of auxiliary interrupter 128 accommodates an electrically conductive resistor probe 178. Probe 178 has an opening 180 for accommodating bayonet contact 23. Resistor probe 178 extends outside of interrupter 28 and is electrically and mechanically connected to one end of surge limiting resistor 32. The other end of resistor 32 is electrically and mechanically connected to platform casting 24.

A tubular member 182 extends between stationary contact 150 and resistor probe 178 and accommodates the passage of bayonet contact 23.

Auxiliary interrupter 128 operates internally in the following manner. Assuming that it is in the closed position with bayonet contact 23 fully inserted, then the bayonet occupies the position shown in phantom n FIG. and is in electrical contact with stantionary contact 150 and resistor probe 178. In addition, bayonet 23 effectively blocks nozzle 149 and opening 155 and maintains push rod 166 and piston 156 in upwardly biased position.

As bayonet contact 23 moves from closed to open position, it permits piston 156 and push rod 166 to be biased downwardly by biasing spring 162. Downward movement of piston 156 continues until the oil refill parts 147 are blocked thereby and the ports 158 are closed by cooperation with contact housing 153. Push rod 166 moves downwardly simultaneously until it extends through control housing 153 and into tubular member 182 thereby efiectively sealing the tubular member against oil flow therethrough. It will be noted that ball 170 prevents oil flow downwardly through passage 168 into tubular member 182. As will be understood, separation of bayonet contact 23 and stationary contact 150 is not accompanied by arcing. As bayonet contact 23 continues its downward movement through tubular member 182, a partial vacuum or low pressure condition exists therein. As bayonet contact 23 leaves the end of tubular member 182 and disengages probe 178, arcing occurs. However, after bayonet contact 23 is clear of tubular member 182, oil beneath piston 156 is able to move up into tubular member 182 and does so as piston 156 resumes its descent. This flow of oil past probe 178 aids in arc extinction. The oil flowing up tubular member 182 goes through passage 168 in push rod 166, past ball 170 and out through vent 160 in piston 156. As bayonet contact 23 unblocks nozzle 149 oil is "forced by piston 156 through the nozzle transversely to the are still existing between probe 178 and bayonet contact 23. As bayonet contact 23 subsequently unblocks opening 155 oil is forced by piston 156 through opening 155 in axial alignment with and through any are still existing between probe 178 and bayonet contact 23.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a circuit interrupter,

a main interrupter having a stationary main contact therein,

an auxiliary interrupter having a stationary auxiliary contact and an electrically conductive probe therein,

said stationary contacts being electrically connected to each other,

a shunt resistor having one end electrically connected to said stationary contacts and having its other end electrically connected to said probe,

a movable main contact for cooperation with said stationary main contact, and a movable auxiliary con tact for cooperation with said probe and said stationary auxiliary contact,

said movable main and movable auxiliary contacts being electrically connected and being adapted so that upon movement thereof to closed position, said movable auxiliary contact first engages said probe, then said movable main contact engages said stationary main contact, and then said movable auxiliary contact engages said stationary auxiliary contact.

2. A circuit interrupter according to claim 1 wherein said main interrupter has an electrically conductive member therein and further comprising another shunt resistor having one end electrically connected to said stationary contacts and having its other end electrically connected to said member.

said movable main and movable auxiliary contacts being adapted so that upon movement thereof to closed position said movable main contact first engages said member, then said movable auxiliary contact engages said probe, then said movable main contact engages said main stationary contact, and then said movable auxiliary contact engages said stationary auxiliary contact.

3. In a circuit interrupter,

a line terminal, an electrically conductive platform member depending from said line terminal,

a main interrupter having a stationary main contact therein electrically connected to said member,

an auxiliary interrupter depending from said member,

said auxiliary interrupter having a stationary auxiliary contact therein electrically connected to said member and having an electrically conductive probe therein,

a shunt resistor depending from said member and having one end electrically connected to said member and having its other end electrically connected to said probe,

a movable electrically conductive bridge,

a movable main contact on said bridge for cooperation with said stationary main contact, and a movable auxiliary contact on said bridge for cooperation with said probe and said stationary auxiliary contact,

:said movable main contact and said movable auxiliary contact being adapted so that upon movement of said bridge to closed position said movable auxiliary contact engages said probe, then said movable main contact engages said stationary main contact,

and then said movable auxiliary contact engages said stationary auxiliary contact.

4. A circuit interrupter according to claim 3 wherein said main interrupter has an electrically conductive portion and further comprising another shunt resistor depending from said member and having one end electrically connected to said member and having its other end electrically connected to said electrically conductive portion,

said movable main contact and said movable auxiliary contact being adapted so that upon movement of said bridge to closed position said movable main contact first engages said electrically conductive portion then said movable auxiliary contact engages said probe, then said movable main contact engages said stationary main contact, and then said movable auxiliary contact engages said stationary auxiliary contact.

5. In a circuit interrupter,

a pressure confining structure having a chamber therein,

said structure having a fluid refill port, a discharge nozzle and an opening communicating with said chamber,

relatively stationary contact means located in said chamber,

a conductive probe located in said chamber between said stationary contact means and said opening,

a spring biased piston in said chamber,

and a movable contact movable to closed position wherein it engages said stationary contact and said probe and blocks said opening and said nozzle and wherein said movable contact maintains said piston to its biased position,

said movable contact also being movable toward open position whereby it disengages from said stationary contact and causes said piston to block said refill port until said movable contact disengages said probe and unblocks said nozzle, whereupon said piston forces fluid from said chamber through said nozzle and subsequently through said opening to extinguish arcing between said probe and said movable contact.

6. A circuit interrupter according to claim 5 having a push rod abutting said piston and wherein said movable contact acts on said push rod to move said piston to its biased position.

7. In a circuit interrupter,

a pressure confining structure having a chamber therein,

said structure having an opening at one end communicating with said chamber,

said structure having a fluid refill port in a side thereof communicating with said chamber and having a discharge nozzle in a side thereof communicating with said chamber,

relatively stationary contact means located in said chamber, a conductive probe located in said chamber between said stationary contact means and said open- 3,

a spring biased piston in said chamber,

a push rod abutting said piston,

and a bayonet type movable contact movable to closed position wherein it engages said stationary contact and said probe and blocks said opening and said nozzle and wherein said movable contact acts on said push rod to move said piston to its biased position, said movable contact also being movable toward open position whereby it disengages from said stationary contact and causes said piston to block said refill port until said movable contact disengages from said probe and unblocks said nozzle, whereupon said piston forces fluid from said chamber through said nozzle and through said opening to extinguish arcing between said probe and said movable contact.

8. A circuit interrupter according to claim 7 wherein said piston has a vent therethrough and said push rod has a passage therethrough aligned with said vent and further comprising a one way valve for preventing fluid flow through said passage toward said bayonet contact,

and a hollow tubular member located between said relatively stationary contact and said probe,

said bayonet contact in its closed position extending through said tubular member, said bayonet contact being movable from closed position toward open position and thereby disengages from said stationary contact and causes said piston to move to block said refill port and remain stationary until said bayonet contact withdraws from said tubular member and disengages from said probe whereupon said piston forces fluid through said passage, through said one way valve and through said vent to aid in arc extinction. 9. In a circuit interrupter, a pressure confining structure having a chamber therein, said structure having an opening at one end and a fluid refill port and discharge nozzle in the sides thereof all communicating with said chamber,

relatively stationary contact means comprising a contact housing located in said chamber,

a bayonet contact for cooperation with said stationary means and movable through the housing thereof,

a conductive probe located in said chamber between said stationary contact means and said opening,

a spring biased piston in said chamber,

said piston having a vent therethrough,

a push rod abutting said piston and for cooperation with said bayonet contact and having a passage therethrough aligned with said vent,

a one way valve including a ball located in said passage for preventing fluid flow through said passage toward said bayonet contact,

and a hollow tubular member located between said relatively stationary contact and said probe and aligned with said stationary contact housing,

said bayonet contact having a closed position wherein it extends into said chamber to block fluid flow through said opening and said nozzle and wherein it makes electrical contact with said probe and said stationary contact and wherein it extends through said tubular member and acts on said push rod to maintain said piston in its biased position,

said bayonet contact being movable from closed position toward open position and thereby disengages from said stationary contact and causes said piston to move to block said refill port and remain stationary until said bayonet contact withdraws from said tubular member and disengages from said probe Whereupon said piston forces fluid through said passage, through said one way valve and through said vent to aid in arc extinction,

said bayonet contact being further movable toward open position to unblock said nozzle and said opening whereupon said piston forces fluid from said chamber through said nozzle and through said opening to aid in extinguishing arcing between said probe and said movable contact.

FOREIGN PATENTS 12/1921 Germany. 1/1930 Germany.

ROBERT S. MACON, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 393 285 July 16 1968 William E. Harper It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8, after line 6, insert a main interrupter depending from said member, line 7, "a" should read said Signed and sealed this 6th day of January 1970.

SEAL) Quest: i

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER,-*J&

\ttesting Officer I Commissioner of Patents 

1. IN A CIRCUIT INTERRUPTER, A MAIN INTERRUPTER HAVING A STATIONARY MAIN CONTACT THEREIN, AN AUXILIARY INTERRUPTER HAVING A STATIONARY AUXILIARY CONTACT AND AN ELECTRICALLY CONDUCTIVE PROBE THEREIN, SAID STATIONARY CONTACTS BEING ELECTRICALLY CONNECTED TO EACH OTHER, A SHUNT RESISTOR HAVING ONE END ELECTRICALLY CONNECTED TO SAID STATIONARY CONTACTS AND HAVING ITS OTHER END ELECTRICALLY CONNECTED TO SAID PROBE, A MOVABLE MAIN CONTACT FOR COOPERATION WITH SAID STATIONARY MAIN CONTACT, AND A MOVABLE AUXILIARY CONTACT FOR COOPERATING WITH SAID PROBE AND SAID STATIONARY AUXILIARY CONTACT, SAID MOVABLE MAIN AND MOVABLE AUXILIARY CONTACTS BEING ELECTRICALLY CONNECTED AND BEING ADATPED SO THAT UPON MOVEMENT THEREOF TO CLOSED POSITION, SAID MOVABLE AUXILIARY CONTACT FIRST ENGAGES SAID PROBE, THEN SAID MOVABLE MAIN CONTACT ENGAGES SAID STATIONARY MAIN CONTACT, AND THEN SAID MOVABLE AUXILIARY CONTACT ENGAGES SAID STAIONARY AUXILIARY CONTACT. 